Plasma processing apparatus

ABSTRACT

A plasma processing apparatus provided with a holding stage of a system in which a temperature of an electrode block is controlled so as to control the temperature of a semiconductor wafer. The electrode block is provided with at least first and second independent temperature controllers on inner and outer sides thereof, and a slit for suppressing heat transfer is provided in the electrode block between the first and second temperature controllers.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a continuation of U.S. application Ser. No. 10/083,381,filed Feb. 27, 2002, the subject matter of which is incorporated byreference herein.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a plasma processing apparatusapplied to microfabrication in semiconductor fabricating processes orthe like and, more particularly, to a plasma processing apparatusprovided with a holding stage on which a semiconductor wafer is to beplaced.

[0003] With the trend toward high integration design of semiconductordevices becoming remarkable in recent years, ever-increasingminiaturization of circuit patterns has been demanded and dimensionalfabrication accuracy required has been increasingly severe. Moreover, atthe same time, it has become necessary to meet requirements for improvedthroughput and larger areas of workpieces to be treated and thetemperature controllability of semiconductor wafers during processinghas become very important.

[0004] For example, in an etching process that requires a high aspectratio (fine and deep trenches), anisotropic etching is required and inorder to realize this, a process in which etching is performed whileprotecting side walls with an organic polymer is adopted and, in thiscase, the generation of an organic polymer that provides protectivefilms varies depending on temperature. If the temperature within asemiconductor wafer during etching processing is nonuniformlydistributed, the degree of formation of side wall protecting filmsvaries in the wafer plane, with the result that etching shape also maysometimes become nonuniform, thus posing a problem.

[0005] Also, there is a case where reaction products adhere to etchedsurfaces again, thereby lowering etching rates. The reaction productsare apt to be distributed more at the center of a semiconductor waferthan near the outer periphery of the semiconductor wafer, with theresult that the etching rate is lower at the center of the semiconductorwafer than near the outer periphery and, therefore, the etching shapewithin the semiconductor wafer plane deviates.

[0006] In order to improve this, it is effective to adopt a method bywhich the re-adhering of reaction products is suppressed by raising thetemperature near the center of a wafer in comparison with thetemperature near the outer periphery. Therefore, as described above, itis necessary to control the semiconductor wafer temperature duringplasma etching so that it is uniform in the wafer plane or to cancel outthe distribution of reaction products by intentionally raising thetemperature in the plane of a semiconductor wafer at the center or nearthe outer periphery.

[0007] Incidentally, it is a general practice to realize thesemiconductor wafer temperature control during processing by controllingthe surface of an electrostatic chuck (a holding stage) on which thewafer to be treated is placed, and as a method of temperature controlfor such a semiconductor wafer during processing, a technique disclosedin JP-A-2000-216140 (prior art 1), for example, can be mentioned.

[0008] In this prior art 1, there is disclosed a structure such that aplurality of independent coolant flow paths capable of controlling theflow rate of coolant are provided within an electrostatic electrodeblock that constitutes a holding stage and the electrode block surfaceis coated with a dielectric film.

[0009] Furthermore, in JP-A-9-17770 (prior art 2) is disclosed astructure such that in order to control the in-plane temperaturedistribution of a semiconductor wafer, two systems of coolant flow pathare provided on concentric circles in the interior of an electrostaticchuck, whereby a relatively low-temperature coolant is caused tocirculate in an outer coolant flow path and a relativelyhigh-temperature coolant is caused to circulate in an inner coolant flowpath. In JP-A-845909 (prior art 3) is disclosed a sample bed (a holdingstage) of such a structure that a metal electrode block is divided intoportions, in each of which a coolant flow path or a heater is providedto perform temperature control.

[0010] In the above prior arts, consideration is not given to the flowof heat in an electrostatic chuck and there was a problem in positivelyrealizing a clear temperature distribution.

[0011] For examples, in the prior arts 1 and 2, in order to realize atemperature distribution in which the temperature near the center of asemiconductor wafer during processing is set higher than the temperaturenear the outer periphery of the wafer, the temperature or flow rate of acoolant is controlled. However, a clear in-plane temperaturedistribution cannot be obtained because of the thermal conductivity ofthe electrode block and, at the same time, because coolant flow pathsare adjacent to each other, the temperature is made uniform within theelectrode block, making it further impossible to obtain a cleartemperature distribution.

[0012] On the other hand, in the electrostatic chuck disclosed as theprior art 3, independent temperature control is possible within dividedelectrode blocks and in-plane temperature distribution control isaccomplished. However, because there is a gap between the blocks, it isdifficult to form dielectric films of thin film thickness with goodreliability.

[0013] Also, in the prior art 1, the electrode is fixed by means ofscrews only in the circumferential part and, therefore, the electrodeblock is deformed in convex shape by the pressure of the coolant, withthe result that in some cases it is impossible to uniformly adsorb thesemiconductor wafer and an undesired temperature distribution isgenerated in the plane of the semiconductor wafer.

SUMMARY OF THE INVENTION

[0014] The object of the invention is to provide a plasma processingapparatus capable of positively controlling the temperature distributionof a semiconductor wafer during etching processing in a clear state.

[0015] The above-described object can be achieved by using a plasmaprocessing apparatus provided with a holding stage of a method by whichthe temperature of an electrode block is controlled thereby to controlthe temperature of a semiconductor wafer. In this holding stage, theelectrode block is provided with independent temperature control meanson the inner and outer sides and, at the same time, a slit forsuppressing heat transfer is provided between these temperature controlmeans.

[0016] In this plasma processing apparatus, the above-described slit forsuppressing heat transfer may be formed almost concentrically.

[0017] Also, the above-described object can be achieved by using aplasma processing apparatus, in which the above-described independenttemperature control means on the inner and outer sides may comprise: afirst flow path and a second flow path, which are provided in theelectrode block independently on the inner and outer sides of theelectrode block; and first heat-medium supply means and secondheat-medium supply means, which independently supply to these first andsecond flow paths a heat medium, for which at least either oftemperature and flow rate is controlled. Similarly, the above-describedobject can be achieved by using a plasma processing apparatus, in whichabove-described independent temperature control means on the inner andouter sides may comprise: a first flow path and a second flow path,which are provided in the above-described electrode block independentlyon the inner and outer sides of the electrode block; first heat-mediumsupply means and second heat-medium supply means, which commonly supplyto these first and second flow paths a heat medium, for which at leasteither of temperature and flow rate is controlled; and temperatureadjustment means provided in a conduit that connects the above-describedfirst and second flow paths together.

[0018] Furthermore, the above-described temperature adjustment means maybe constituted by a heater, and this heater may be provided on thebackside of the above-described electrode block or may be built in theabove-described electrode block.

[0019] Next, the above-described electrode block may be provided, on itssurface, with a dielectric film, and a heater may be built within thedielectric film. The above-described heater may serve also as anelectrostatic chuck.

[0020] Also, the above-described electrode block may comprise one memberin which the above-described heat-medium flow paths are formed and theother member for ensuring the rigidity of the above-described electrodeblock, and these members may be fastened in one piece. Means forfastening the above-described two members may be any of screwing,brazing, diffusion bonding and electron beam welding. Moreover, themember for ensuring rigidity may be made of a material with a lowerthermal conductivity than the above-described electrode block.

[0021] Or the above-described first and second flow paths may be eachformed from a pipe with a circular section or a polygonal shape attachedto the above-described electrode block. Moreover, the above-describedpipe may be built in the above-described electrode block.

[0022] Also, the above-described electrode block may be provided with atleast three temperature sensors and temperature control may be performedon the basis of information from these temperature sensors. Theabove-described electrode block may be provided, on its surface, with adielectric film and may be constructed as an electrostatic chuck inwhich a gas for heat transfer is introduced to between theabove-described dielectric film and the above-described semiconductorwafer.

[0023] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is an explanatory drawing of an embodiment of a plasmaprocessing apparatus according to the invention;

[0025]FIG. 2 is a perspective view of an embodiment of an electrostaticchuck in a plasma processing apparatus according to the invention;

[0026]FIG. 3 is an explanatory drawing of the slit arrangement state inanother embodiment of an electrostatic chuck according to the invention;

[0027]FIG. 4 is explanatory drawing of the alit arrangement state in afurther embodiment of an electrostatic chuck according to the invention;

[0028]FIG. 5 is a characteristic diagram of an example of pressuredistribution of helium gas between an electrostatic chuck and asemiconductor wafer;

[0029]FIG. 6 is a characteristic diagram of an example of the surfacetemperature of a semiconductor wafer by an electrostatic chuck;

[0030]FIG. 7 is a characteristic diagram of an example of the surfacetemperature of a semiconductor wafer in an embodiment of anelectrostatic chuck according to the invention as compared with priorart;

[0031]FIG. 8 is a characteristic diagram of an example of the surfacetemperature of a dielectric film in an embodiment of an electrostaticchuck according to the invention as compared with prior art;

[0032]FIG. 9 is a sectional view of the second embodiment of anelectrostatic chuck according to the invention;

[0033]FIG. 10 is a sectional view of the third embodiment of anelectrostatic chuck according to the invention;

[0034]FIG. 11A is an explanatory drawing of an example of deformationthat occurs in an electrode block of an electrostatic chuck according tothe invention, which shows a state before deformation;

[0035]FIG. 11B is an explanatory drawing of an example of deformationthat occurs in an electrode block of an electrostatic chuck according tothe invention, which shows a state after deformation;

[0036]FIG. 12 is an explanatory drawing of another example ofdeformation that occurs in an electrode block of an electrostatic chuckaccording to the invention;

[0037]FIG. 13 is a sectional view of the fourth embodiment of anelectrostatic chuck according to the invention; and

[0038]FIG. 14 is a sectional view of the fifth embodiment of anelectrostatic chuck according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] A plasma processing apparatus according to the invention will bedescribed below in detail with the aid of the illustrated embodiments.

[0040]FIG. 1 shows an embodiment of a plasma processing apparatus Paccording to the invention, and FIG. 2 is a perspective view, partiallyin section, of an electrostatic chuck S, which is used in this plasmaprocessing device as a holding stage S for a semiconductor wafer W.Incidentally, this holding stage is generally called an electrostaticchuck and hence is hereinafter referred to as an electrostatic chuck S.

[0041] And in the case of the electrostatic chuck S related to thisembodiment, as will be described later with the aid of FIGS. 3 and 4,flow paths for a fluid (a heat medium) that works as a coolant or heatmedium and, as shown in FIG. 1, this electrostatic chuck S is installedand used in a plasma processing device related to an embodiment of theinvention.

[0042] As shown in FIG. 2, this electrostatic chuck S is constituted byan electrode block 1 made of aluminum having a thickness of 25 mm, aguide member 2 made of a stainless steel having a thickness of 10 mm, abase member 3 having a thickness of 10 mm, a dielectric film 4, and anelectrode cover 5 made of ceramics, and is fabricated to have a diameterof 320 mm and a total thickness of 45 mm when it is intended for use ina semiconductor wafer of 12 inches (300 mm) in diameter, for example.

[0043] First, as shown in FIG. 3, on the undersurface of the electrodeblock 1 are formed flow-path slits 11, 12 that are disposed in spiralform in such a manner that the two constitute, respectively, a slit onthe inside diameter side and a slit on the outside diameter side, andbetween the two slits 11, 12 is formed an almost concentric slit forsuppressing heat transfer 13 (radius=90 mm, width=5 mm, height(depth)=18 mm).

[0044] And upon the undersurface of this electrode block 1 is superposedthe guide member 2, and the open portions of each slit 11, 12, 13 areblocked by fixing the guide member 2 with bolts 6. A gas introductionhole 7 is provided in such a manner that the gas introduction hole 7passes through the electrode block 1 and guide member 2 including thebase member 3.

[0045] Next, the dielectric film 4 is formed, for example, fromhigh-purity alumina ceramics and its thickness is 0.1 mm. However, thematerial and thickness of this dielectric film 4 are not limited to thisexample and in the case of synthetic resins, for example, a thicknessfrom 0.1 mm to a few millimeters can be selected according to thedielectric constant of the material.

[0046] And as shown in FIG. 2, this dielectric film 4 is provided with alinear slit 41, which extends radially while communicating with the gasintroduction hole 7, and a plurality of concentric slits 42 thatcommunicate with this linear slit 41, whereby it is ensured that whenthe semiconductor wafer W is placed on the electrostatic chuck S, heliumgas is introduced from the gas introduction hole 7 into a gap betweenthe dielectric film 4 and the semiconductor wafer W.

[0047] Each of the flow-path slits 11, 12 of the electrode block 1 isprovided with introduction portions 11A, 12A and discharge portions 11B,12B for a coolant (or a heat medium), whereby each of the flow-pathslits 11, 12 can work as mutually independent heat-medium flow paths forthe passage of a coolant for temperature control. And the introductionportions 11A, 12A and discharge portions 11B, 12B of each of theflow-path slits 11, 12 are connected to coolant supply units 51, 52,which are respectively independent, so that at least either of the flowrate and temperature of the coolant to be circulated to each of theflow-path slits 11, 12 can be individually adjusted.

[0048] The arrangement of the flow-path slits 11, 12 is not limited tothe spiral shape shown here. For example, FIG. 4 shows a case where theflow-path slits 11, 12 are each arranged in a plurality of concentriccircles, and in this case a coolant flows in semicircular directionsthat are mutually counter directions.

[0049] Next, the operation of a plasma processing apparatus according tothis embodiment will be described. First, the electrostatic chuck S isinstalled within the processing chamber shown in FIG. 1, thesemiconductor wafer W is placed on the electrostatic chuck S, achlorine-based or fluorine-based gas is introduced, the atmosphere inthe processing chamber is irradiated with a microwave 9 generated by amagnetron 8 thereby to excite a plasma, and the distribution and densityof the plasma are controlled by a magnetic field generated by solenoidcoils 10.

[0050] And at the same time, etching is performed by applying a DCcurrent and a high frequency to the electrode block 1 of electrostaticchuck S (FIG. 2) while controlling the temperature of the semiconductorwafer W.

[0051] Incidentally, the embodiment of the plasma processing apparatusaccording to the invention is not limited to the method based on the useof a magnetron described here, and a plasma processing device of othermethods may be used.

[0052] Next, for the operation of the electrostatic chuck in thisembodiment, the principle of temperature control will be first describedbelow.

[0053] First, this electrostatic chuck S adsorbs the semiconductor waferW by a Coulomb force or a Johnsen-Rahbeck force that is generated by theapplication of a high voltage to the dielectric film 4. There are twotypes of methods of application of a high voltage, i.e., the unipolartype and bipolar type. In the unipolar type, a uniform voltage isapplied across the semiconductor wafer and the dielectric film, whereasin the bipolar type, two or more kinds of electric potentials areapplied across the semiconductor wafer and the dielectric film. In thisembodiment, either of the two types may be used.

[0054] After adsorption, as described above, helium gas for heattransfer (usually, 1000 Pa or so) is introduced from the gasintroduction hole 7 into a gap between the semiconductor wafer W and thedielectric film 4. The temperature of the semiconductor wafer W isgoverned by the heat input from the plasma, the overall heat transfercoefficient of the gap filled with He gas, the thermal resistance of theelectrode block 1, and the overall heat transfer coefficient between thecoolant that is caused to circulate into the electrode block 1 and theelectrode block 1.

[0055] Therefore, the control of the temperature of the semiconductorwafer W can be performed either by installing a mechanism for changingthe pressure of helium gas on the electrostatic chuck S, the temperatureof the coolant, the flow rate of the coolant (a change in the overallheat transfer coefficient between the coolant and the electrode block)or by installing a second temperature adjustment mechanism such as aheater.

[0056] For example, in a case where the size of the flow-path slits 11,12 is 5 mm width×16 mm height, it has been ascertained that if the flowrate of a coolant at 20° C. is doubled from 2 l/min to 4 l/min, then theoverall heat transfer coefficient between the coolant and the electrodeblock 1 increases from about 200 W/m2K to about 400 W/m2K. Therefore,because the overall heat transfer coefficient can be increased byincreasing the flow rate of the coolant, a temperature rise of theelectrode block 1 can be held to a low level even if the heat input fromthe plasma increases.

[0057] Incidentally, in a general electrostatic chuck, for reasons ofits structure a temperature distribution occurs in the plane of asemiconductor wafer as described below in spite of uniform heat inputfrom a plasma. Because the pressure of helium gas introduced into a gapbetween the semiconductor wafer and a dielectric film is higher than thepressure in the chamber (processing chamber) during the generation of aplasma, the gas leaks from the outermost peripheral part of thesemiconductor wafer W. The measured volume of leaking gas is 2 to 5ml/min.

[0058]FIG. 5 shows an example of calculation result of helium gaspressure. In this graph are shown calculated values of pressuredistribution on the backside of a semiconductor wafer found from theleak rate of helium gas. As shown in this figure, because the helium gaspressure at the outermost periphery of the semiconductor wafer is higherthan the chamber pressure during the generation of a plasma, the heliumgas pressure drops abruptly at the outer periphery of the semiconductorwafer.

[0059] Next, FIG. 6 shows the surface temperature of the semiconductorwafer W in a case where heat input is uniform in the plane of thesemiconductor wafer. In FIG. 1 are shown results obtained in a casewhere a plasma is generated in an atmosphere into which a fluorine-basedgas (pressure 1 Pa) is introduced by use of the plasma processingapparatus shown in FIG. 1 and where the flow rate of the coolant is setat 5 l/min and the temperature of the coolant is set at 35° C. Theabscissa indicates the distance from the center of the semiconductorwafer and the ordinate indicates the temperature of the semiconductorwafer surface. The mark  denotes measured values and the solid linerepresents calculated values.

[0060] Therefore, from FIGS. 5 and 6, it is apparent that the surfacetemperature of the semiconductor is higher at the outermost peripherythan at the center.

[0061] Next, the temperature difference in the plane of thesemiconductor wafer, which is denoted by ΔT, depends mainly onhigh-frequency electric power applied to the electrostatic chuck, andreached about 10° C. when power of 1300 W, for example, was applied.

[0062] Therefore, in order to give a gentle temperature distribution(for example, the temperature at the center or at the periphery is high)on the plane of the semiconductor wafer by means of the electrostaticchuck, it is necessary to control the temperature distribution inconsideration of the pressure distribution of helium gas.

[0063] Incidentally, the foregoing applies to general electrostaticchucks including prior art. Next, an explanation will be given to theelectrostatic chuck S related to the embodiment of the invention shownin FIG. 1. In this embodiment, the electrode block 1 that constitutesthis electrostatic chuck S is provided with the slit for suppressingheat transfer 13 in such a manner that the slit 13 defines a boundarybetween the inner and outer peripheral parts of the electrode block 1.

[0064] Furthermore, in this electrostatic chuck S, the electrode block 1is provided with the independent flow-path slit 11 and flow-path slit 12in such a manner that the flow-path slits 11 and 12 sandwich the slitfor suppressing heat transfer 13 on the inner and outer peripheralsides, and at least either of the flow rate and temperature of thecoolant can be individually adjusted.

[0065] The slit for suppressing heat transfer 13 is kept blocked by theguide member 2 as described above and, therefore, the interior of theslit for suppressing heat transfer 13 is filled with an atmosphere at apressure almost equal to the pressure in the processing chamber or iskept in a vacuum. For this reason, the slit for suppressing heattransfer 13 suppresses heat transfer between the inner and outerperipheral sides of the electrode block 1, thus allowing a largetemperature difference between the two sides to occur.

[0066]FIG. 7 shows an example of measurement of the surface temperaturedistribution of a semiconductor wafer W obtained under the sameconditions as in FIG. 6 by use of an electrostatic chuck S that isprovided, in the electrode block 1, with the slit for suppressing heattransfer 13. In this example, a case where the temperature in the centerpart is set relatively higher than the temperature in the outerperipheral part is supposed. In this example, the high-frequencyelectric power applied to the electrostatic chuck is 100 to 1300 W, thecoolant flow rate in the slit 11 is 1 to 4 l/min, and the coolant flowrate in the slit 12 is 4 to 8 l/min.

[0067] As shown in FIG. 7, it is apparent that in the electrostaticchuck S that is provided with the slit for suppressing heat transfer 13as one embodiment of the invention, the temperature in the center partcan be raised sufficiently high while holding the temperature of theoutermost peripheral part of the surface of the semiconductor wafer W toa low level.

[0068] Next, FIG. 8 shows the result of an analysis of the surfacetemperature of the dielectric film 4. As shown in the figure, the slitfor suppressing heat transfer 13 is provided also in this case and,therefore, the temperature distribution of the surface of dielectricfilm 4 is remarkable. Therefore, it is apparent that a very distincttemperature distribution was obtained. It is also apparent that thetemperature distribution changes greatly on both sides of the slit forsuppressing heat transfer 13.

[0069] In this type of electrostatic chuck, as described above, it is ageneral phenomenon that the helium gas pressure is low in the outermostperipheral part of the semiconductor wafer and that the temperature ishigh in the outermost peripheral part of the semiconductor wafer.Therefore, in the case of this embodiment, in order to hold thetemperature of the outermost peripheral part of the semiconductor waferW to a low level and, at the same time, to raise the temperature in thecenter part, it is necessary to install the slit for suppressing heattransfer 13 in an appropriate position.

[0070] In this embodiment, good results were obtained by setting theposition of the slit for suppressing heat transfer 13 intended for use,for example, in the above-described semiconductor wafer with a diameterof 300 mm in the range of 80 to 120 mm from the center. In the case of asemiconductor wafer W having a diameter of 200 mm, this range is 60 to80 mm.

[0071] Therefore, as is apparent from these results, in theelectrostatic chuck S according to the embodiment of the invention, itis preferred that the slit for suppressing heat transfer 13 be providedin the range of 50 to 80% of the radius of the electrode block 1.

[0072] Incidentally, a temperature distribution desired forsemiconductor wafers in plasma processing is usually a gentlecircumferential distribution in which the temperature in the center partor in the outer peripheral part is high, and for this reason, it ispreferred that the slit for suppressing heat transfer 13 ofelectrostatic chuck S be concentrically formed.

[0073] On the other hand, it is preferred that the sectional shape ofthis slit for suppressing heat transfer 13 be rectangular, trapezoidal,etc. from the standpoint of fabrication. It is the dimension of heightof the sectional shape that is important, and the higher the height,that is, the more the height of the slit for suppressing heat transfer13.

[0074] The more the effect of this slit to suppress heat transfer willincrease. However, when the height of the slit for suppressing heattransfer 13 increases in this manner, the rigidity of the electrodeblock 1 decreases. In this case, therefore, a rib may be provided in theslit thereby to prevent a decrease in the rigidity of the electrodeblock 1.

[0075] Therefore, according to this embodiment of the invention, it ispossible to clearly control the temperature distribution of thesemiconductor wafer W during plasma etching, with the result thatthrough arbitrary temperature control it is possible to ensure a uniformtemperature in the plane of the semiconductor wafer or a temperaturedistribution in a clear state, such as a temperature distributionpattern in which the temperature in the center portion or a temperaturedistribution pattern in which the temperature in the outer peripheralportion is high. As a result, this embodiment of the invention can beeasily applied to plasma processing in which by canceling out thedistribution of reaction products the re-adhering of the reactionproducts to etched surfaces is suppressed, thus contributing greatly toan improvement in the yield of semiconductor wafer processing.

[0076] Next, further embodiments of the invention will be describedbelow. First, FIG. 9 shows an electrostatic chuck in the secondembodiment of the invention. In this embodiment, a slit for suppressingheat transfer 13 is provided in an electrode block 1, a slit 11, whichprovides a coolant flow path on the inner peripheral side, and a slit12, which provides a coolant flow path on the inner peripheral side, areconnected in series by means of a conduit 14, and an electric heater 15is provided in this conduit 14 to constitute an electrostatic chuck S1.

[0077] And in this electrostatic chuck S1, a coolant is supplied fromone coolant supply unit 53 commonly to the slit 11 and slit 12, whichare the coolant flow paths in the electrode block 1. During coolantsupply, the temperature is controlled by a power controller, which isnot shown in the figure, and the heater 15 works to heat the coolantflowing through the conduit 14 to a prescribed temperature.

[0078] Therefore, according to this electrostatic chuck S1, by adjustingthe heating temperature of the coolant by the heater 15, the temperaturedistribution of the semiconductor wafer W can be easily changed to atemperature distribution pattern in which the temperature in the centerpart is high or a temperature distribution pattern in which thetemperature in the outer peripheral part is high.

[0079] That is, when the temperature distribution of the semiconductorwafer W is to be changed to a temperature distribution pattern in whichthe temperature in the center part is high, it is necessary only thatthe heating temperature of the coolant by the heater 15 be controlled bycausing the coolant to circulate in the direction indicated bysolid-line arrows. Conversely, when the temperature distribution of thesemiconductor wafer W is to be changed to a temperature distributionpattern in which the temperature in the outer peripheral part is high,it is necessary only that the coolant be caused to circulate in thedirection indicated by dotted-line arrows.

[0080] Therefore, also through the use of this electrostatic chuck S1 aswith the electrostatic chuck S described in FIGS. 1 to 4, it is possibleto clearly control the temperature distribution of the semiconductorwafer W during plasma etching, with the result that through arbitrarytemperature control it is possible to ensure a uniform temperature inthe plane of the semiconductor wafer or a temperature distribution in aclear state, such as a temperature distribution pattern in which thetemperature in the center portion or a temperature distribution patternin which the temperature in the outer peripheral is high. As a result,this embodiment of the invention can be easily applied to plasmaprocessing in which by canceling out the distribution of reactionproducts the re-adhering of the reaction products to etched surfaces issuppressed, thus contributing greatly to an improvement in the yield ofsemiconductor wafer processing.

[0081] In addition, according to this electrostatic chuck S1,installation of one coolant supply unit 53 is sufficient and, therefore,the composition of the apparatus can be simplified.

[0082] Also, in the case of this electrostatic chuck S1, installation ofthe heater 15 within the conduit 14 enables space to be effectivelyutilized and this construction is very effective also from thestandpoint of thermal efficiency.

[0083] Incidentally, in the embodiment shown in FIG. 9, the descriptionwas made about a case where the heater 15 is of the electric heatingtype. However, a Peltier element may be used as the heater 15 and inthis case, it is possible not only to heat the coolant in the conduit14, but also cool to this coolant.

[0084] Next, FIG. 10 shows the third embodiment of the invention. Inthis embodiment, a heater 15 is built in an electrode block 1 toconstitute an electrostatic chuck S2. In this embodiment, the heater 15is cast in the electrode block 1 by use of casting technology. Theheater 15 used in this case is a heater fabricated by housing a nichromewire or tungsten wire sheathed with an insulating material, such asalumina in a stainless steel tube or a carbon steel, which is called asheathed heater, etc.

[0085] Also, the heater 15 may be of a film structure formed by usingmultiple layers of dielectric film 4 in which a tungsten film issandwiched by outer layers, for example, an alumina/tungsten/aluminastructure, and in this case, the construction may be such that a heaterof tungsten further serves as the component electrode of anelectrostatic chuck.

[0086] According to the above embodiment, because the slit forsuppressing heat transfer 13 is provided in the electrode block 1, thetemperature of the semiconductor wafer W can be arbitrarily controlledand, at the same time, thermal efficiency can also be dramaticallyimproved. However, it might be thought that the rigidity of theelectrode block 1 is decreased by providing the slit for suppressingheat transfer 13.

[0087] Therefore, next, an explanation will be given to this embodimentof the invention in which a decrease in rigidity due to the providing ofthis slit is suppressed concerning the case of the electrostatic chuck Sshown in FIG. 1. In this case, as shown in FIG. 11A, the electrostaticchuck S is constituted by an electrode block 1 and a guide member 2. Andin this guide member 2, an O-ring 16 is fitted in the outermostperipheral part and the guide member 2 is tightened to the electrodeblock 1 by means of blots 6, although this is omitted in FIG. 1.

[0088] The pressure P of the coolant that flows through the slits 11, 12is usually 500 KPa or so. However, because this pressure is applied toeach of the slits 11, 12, the electrode block 1 undergoes deformation asdrawn by a broken line in an exaggerated form in FIG. 11B.

[0089] Therefore, in order to cope with such deformation and prevent thedeformation, as shown in FIG. 12, it is necessary only that theelectrode block 1 be tightened by means of another bolt 60 from the backside of the guide member 2 in a position corresponding to half theradius of the electrode block 1. This enables deformation to besuppressed as drawn in an exaggerated form in the figure.

[0090] According to results of measurement, in a case where only theoutermost peripheral part of electrode block 1 with a diameter of 320 mmand a thickness of 25 mm, deformation of 0.5 mm or so was observed inthe center part. However, as shown in FIG. 12, when another bolt 60 wasprovided, deformation scarcely occurred and good results were obtained.

[0091] Incidentally, in the case of the above-described embodiment, anelectrostatic chuck S with a better thermal efficiency can be obtainedby fabricating the electrode block 1 from a material of lower thermalconductivity than the guide member 2. In the above embodiment, thematerial for the electrode block 1 is aluminum and the material for theguide member 2 is stainless steel as described above. This meets theabove conditions. Incidentally, the method of tightening the electrodeblock 1 and the guide member 2 together is not limited to the abovescrewing by means of bolts. Other tightening methods, such as brazing,diffusion bonding and electron beam welding, may also be adopted.

[0092] Next, as still further embodiments of the invention, anexplanation will be given to an electrostatic chuck that is especiallyexcellent in temperature response. First, FIG. 13 shows the fourthembodiment of the invention. In the electrostatic chuck S3 of thisembodiment, instead of forming slits that serve as coolant flow paths inthe electrode block 1, pipes 17, 18 are brazed to the underside of theelectrode block 1. Next, FIG. 14 shows the fifth embodiment of theinvention. In this figure is shown an electrostatic chuck S4 of theinvention in a case where pipes 17, 18 that are brazed after being halfembedded on the underside of an electrode block 1 and heaters 20, 21 areindividually provided, respectively, for the pipes 15, 16.

[0093] In both FIG. 13 and FIG. 14, the pipes 17 form coolant flow pathson the inner peripheral side and the pipes 18 form coolant flow paths onthe outer peripheral side. In these cases, the pipes 17, 18 are formedin square form. The pipes 17, 18 may have an arbitrary polygonalsectional form and of course they may be ordinary round pipes.

[0094] Therefore, first, although the electrostatic chuck S3 shown inFIG. 3 is almost the same as the electrostatic chuck S shown in FIG. 1,this electrostatic chuck S3 is excellent in temperature response becausethe electrode block is thin.

[0095] Also, the electrostatic chuck S4 shown in FIG. 14 is excellent intemperature response. In this case, because the heaters 20, 21 areprovided on the inner and outer peripheral sides, respectively, of theslit for suppressing heat transfer 13, it is possible to obtain atemperature distribution of finer temperature change by controlling thetemperature by these heaters by means of each power controller 22, 23.As an example, temperature characteristics were measured by causing acoolant to circulate by setting the power supplied to each of theheaters 20, 21 at 300 W and the flow rate of the coolant at 4 l/minute.As a result, it was easy to realize a temperature distribution patternwith a temperature difference of 15° C. in which the temperature in thecenter part is high and a temperature distribution pattern with atemperature difference of 15° C. in which the temperature in the outerperipheral part is high.

[0096] In the electrostatic chucks S3, S4 shown in FIGS. 13 and 14,because the pressure of the coolant acts only on the interior of thepipes 17, 18 and no direct pressure is applied to the electrode block 1,there is no fear of the occurrence of deformation in the electrode block1. In these embodiments, the pipes 17, 18 and heaters 20, 21 may be castinto the electrode block 1.

[0097] Incidentally, although the foregoing applies to the embodimentsin which the number of the slit for suppressing heat transfer 13 that isformed within the block 1 is 1, a plurality of slits for suppressingheat transfer 13 may be provided as required. And in this case, it ispossible to easily realize a temperature distribution with patterns offiner changes and a semiconductor wafer can be controlled to anarbitrary temperature distribution.

[0098] With the above-described embodiments, in controlling theelectrostatic chuck S, etc. to a prescribed temperature distribution, itis necessary that a plurality of temperature sensors be provided withinthe electrode block 1. In this case, as described above, because usuallythe temperature of the outermost peripheral part of the semiconductorwafer shows a tendency to rise relatively in the plane of thesemiconductor wafer, by providing temperature sensors in at least threeplaces between the center of the semiconductor wafer and the outerperiphery part it is possible to perform control while monitoring atemperature distribution pattern in which the temperature in the centerpart is high, a temperature distribution pattern in which thetemperature in the outer peripheral part is high, etc.

[0099] According to the invention, by providing a slit for suppressingheat transfer in an electrode block and independent temperature controlmechanisms that sandwich this slit on the inner and outer peripheries,it has become possible to control the temperature distribution totemperatures that are independent in the plane of the electrode block.As a result, it has become easy to adapt to changes in temperaturedistribution patterns of semiconductor wafer.

[0100] And as a result, it has become possible to accomplish diversifiedprocessing of semiconductor wafers by use of various kinds oftemperature distribution patterns, thus contributing greatly to animprovement in the performance of semiconductor wafers.

[0101] Furthermore, according to the invention, the heat-medium flowpaths are composed of divided members and each divided member istightened by screwing, bracing, diffusion bonding and electron beamwelding. Therefore, it is possible to easily adapt to deformation of theelectrode block by the pressure of the heat medium.

[0102] According to the invention, because the coolant flow paths mayalso be formed from pipes having a circular or polygonal section,general-purpose parts can be used and the heat capacity of the electrodeblock also decreases. Therefore, an electrostatic chuck and a plasmaprocessing apparatus that are excellent in thermal response can beprovided.

[0103] Therefore, according to the plasma processing of this invention,the temperature control of semiconductor wafers can be arbitrarily setand, at the same time, requirements for uniform etching can be easilymet. Therefore, the yield of semiconductor devices can be substantiallyimproved and cost can be sufficiently reduced.

[0104] It should be further understood by those skilled in the art thatthe foregoing description has been made on embodiments of the inventionand that various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and the scope of theappended claims.

What is claimed is:
 1. A plasma processing apparatus provided with aholding stage of a system in which a temperature of an electrode blockis controlled so as to control a temperature of a semiconductor wafer,wherein said electrode block is provided with at least first and secondindependent temperature control means on the inner and outer sidesthereof and, a slit for suppressing heat transfer is provided in saidelectrode block between said first and second independent temperaturecontrol means.
 2. A plasma processing apparatus according to claim 1,wherein said slit for suppressing heat transfer is formed substantiallyconcentrically.
 3. A plasma processing apparatus according to claim 1,wherein a heater is provided on the backside of said electrode block. 4.A plasma processing apparatus according to claim 1, wherein a heater isbuilt in said electrode block.
 5. A plasma processing apparatusaccording to claim 1, wherein said electrode block is provided, on thesurface thereof, with a dielectric film.
 6. A plasma processingapparatus according to claim 1, wherein said electrode block is providedwith temperature sensors and temperature control is performed on thebasis of information from said temperature sensors.